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      1 // This file is part of Eigen, a lightweight C++ template library
      2 // for linear algebra.
      3 //
      4 // Copyright (C) 2010, 2013 Jitse Niesen <jitse (at) maths.leeds.ac.uk>
      5 //
      6 // This Source Code Form is subject to the terms of the Mozilla
      7 // Public License v. 2.0. If a copy of the MPL was not distributed
      8 // with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
      9 
     10 #ifndef EIGEN_STEM_FUNCTION
     11 #define EIGEN_STEM_FUNCTION
     12 
     13 namespace Eigen {
     14 
     15 namespace internal {
     16 
     17 /** \brief The exponential function (and its derivatives). */
     18 template <typename Scalar>
     19 Scalar stem_function_exp(Scalar x, int)
     20 {
     21   using std::exp;
     22   return exp(x);
     23 }
     24 
     25 /** \brief Cosine (and its derivatives). */
     26 template <typename Scalar>
     27 Scalar stem_function_cos(Scalar x, int n)
     28 {
     29   using std::cos;
     30   using std::sin;
     31   Scalar res;
     32 
     33   switch (n % 4) {
     34   case 0:
     35     res = std::cos(x);
     36     break;
     37   case 1:
     38     res = -std::sin(x);
     39     break;
     40   case 2:
     41     res = -std::cos(x);
     42     break;
     43   case 3:
     44     res = std::sin(x);
     45     break;
     46   }
     47   return res;
     48 }
     49 
     50 /** \brief Sine (and its derivatives). */
     51 template <typename Scalar>
     52 Scalar stem_function_sin(Scalar x, int n)
     53 {
     54   using std::cos;
     55   using std::sin;
     56   Scalar res;
     57 
     58   switch (n % 4) {
     59   case 0:
     60     res = std::sin(x);
     61     break;
     62   case 1:
     63     res = std::cos(x);
     64     break;
     65   case 2:
     66     res = -std::sin(x);
     67     break;
     68   case 3:
     69     res = -std::cos(x);
     70     break;
     71   }
     72   return res;
     73 }
     74 
     75 /** \brief Hyperbolic cosine (and its derivatives). */
     76 template <typename Scalar>
     77 Scalar stem_function_cosh(Scalar x, int n)
     78 {
     79   using std::cosh;
     80   using std::sinh;
     81   Scalar res;
     82 
     83   switch (n % 2) {
     84   case 0:
     85     res = std::cosh(x);
     86     break;
     87   case 1:
     88     res = std::sinh(x);
     89     break;
     90   }
     91   return res;
     92 }
     93 
     94 /** \brief Hyperbolic sine (and its derivatives). */
     95 template <typename Scalar>
     96 Scalar stem_function_sinh(Scalar x, int n)
     97 {
     98   using std::cosh;
     99   using std::sinh;
    100   Scalar res;
    101 
    102   switch (n % 2) {
    103   case 0:
    104     res = std::sinh(x);
    105     break;
    106   case 1:
    107     res = std::cosh(x);
    108     break;
    109   }
    110   return res;
    111 }
    112 
    113 } // end namespace internal
    114 
    115 } // end namespace Eigen
    116 
    117 #endif // EIGEN_STEM_FUNCTION
    118